Process for the manufacture of c-nitrosoarylamines



is a well-known process.

Patented July 17, 1951 UNITED STATES PATENT OFFICE PR'OCES'S'FOR THE MANUFACTURE. OF

'C-NITROSOARYLAMINES Stiles M. :Roberts, Easton, Pa., assignor to General Aniline & Film Corporation, New York, N. .Y., a corporation of Delaware "No Drawing. Application December 22, .1949, .Serial No. 134,594

This invention relates to the manufacture lof .c-nitrosoarylamines by nitrosation of the corresponding secondary arylamines and rearrangement of the N-nitroso compound. .More particularly, it relates to a process of effectingthe manufacture 'of the rC-nitrosoarylamines by a :one-step process directlyfrom the corresponding secondary arylamine. This .application is a con- .tinuation-in-part-of my co-pending application Serial No. 666,532, fi-ledMay 1, 1946,'now Patent The rearrangement :of N-nitrosoarylamines to their corresponding carbon nitroso derivatives .It has been described as early as 1886 by ,0. Fischer in connection with the preparation of p-nitroso-N-methylaniline, pnitroso-N-ethylaniline, p-nitroso-N-ethyl-otoluidine, and 4-;ni-trosodiphenylamine in Be- .richte, volume 19, page-2994. reference to thediarylami-nes, it has beenfound ..difiicult to effect the rearrangement of the N- .nitroso derivative .to the C-nitroso compound. It

With particular has generally been necessary to first convert the diarylamine to its N-nitrosoamine derivative with .nitrous acid, isolate this derivative, andthen isomerize it by treatment with anhydrous ethyl .alcoholic hydrochloric acid. The N-nitroso 'derivative is generally dried after isolation before effecting the rearrangement.

I The preparation of the .O-;nitrosodiarylamines, and particularly 4-.nitrosodiphenylami-ne, from the corresponding [secondary diarylamines in one -.o peration Without isolation of anyi-ntermediate accomplished by-O. Fischer, by..mer.ely adding a cold concentrated solution of a metal nitrite to an alcoholic hydrogen chloride suspension or so'lutiono'f the base, butwhen using the diarylamines with the same reactants, Wyler applied strictly anhydrous conditions in order to accomplish the conversion in a single step.

I have .now 'found that the inherently difiiculty convertible diarylamines can be converted to the carbon nitroso derivatives in a single step in a much simpler manner and without the necessity .8.1Claims.; (cr zeo mm of using dimculty obtainable reactants, such as dry hydrogen chloride, absolute alcohol, and dry sodium nitrite, if .phosphorus trichloride (P013) or phosphorus oxychloride (phosphoryl chloride POC13) is substituted for the hydrogen chloride. :Although both reactants are contemplated, the phosphorus .oxychloride is preferred because it vhas a more pronounced and complete activity than the phosphorus trichloride. In this-process I may use commercial grades of 'alcoholsuch as the low molecular weight aliphatic alcohols which normally contain water in percentages of from 1 5. If desired, further amounts or water may be added and, of course, it is not necessary to use dry reaction vessels. There is no loss in yield and, as amatter of fact, improved yields of carbon nitrosodiarylamines of good quality are obtained. The process is carried out in itspreferred manner by introducing the phosphorus trichloride or phosphorus oxychloride into a suspension of the 'diarylamine and an alkali'metal nitrite in a commercial grade of an alcohol, such as methanol, subsequently drowning the reaction mixture in an ice water mixture and finally isolating the carbon nitrosoarylamine by known methods most'suitable to the specific amine employed. In some cases, the product may be 'filtered 'ofi as the hydrochloride following the drowning operation.

This process is not restricted to any particular secondary arylamines but is of particular interest in the case of the diarylamines which are diliculty convertible in a one-step operation "tothe C-nitrosodiarylamines. The process may be applied to any-secondary arylamine capable of undergoing the formation of 'N-nitroso derivatives and rearrangement to C-nitrosoarylamines. Typical examples of compounds which are capable of such rearrangement are: 'diphenylamine, phenyl a-naphthylamine, di-l-naphthylamine, 3-acetylaminodiphenylamine, and 4-ac'etylaminodiphenylamine.

.Althoughit is preferableto add the phosphorus trichloride orphosphorus oxychloride to a suspension of the arylamine and alkalimetal nitrite in an alcohol solution, it is possible to first react the phosphorus trichloride or phosphorus oxy- .chloride Withthe alcohol containing small portions of water and add the arylamine to this mixture, aiterwhich the alkali metal nitrite may be incorporated. The amount of phosphorus trichloride or phosphorus oxychloride required to efiect the conversion may vary, but 'for best results from 1 to 8 mols should be employed per mol of the base. The temperature at which the agent 3 necessary for the nitrosation and rearrangement is added is preferably from to 30 C.

The following examples, in which the parts given are by weight unless otherwise stated, will serve to further illustrate the invention, but are not intended to limit its scope.

Example 1 169 g. of diphenylamine, equal to one gram mol,

is dissolved in 360 g. of methanol (commercial) by Warming to 35-40 C. The solution is cooled to 0-5 C. and

80 g. of finely divided sodium-nitrite is added.

Then over a, period of 2-3 hours 212 g. of phosphorus trichloride is added at 0-5 C. The mixture is stirred at 05 C. for 4-6 hours. The light precipitate becomes darker and finally takes on a reddish-brown color. The mixture is then poured into 3000 cc. of ice water, stirred one hour, filtered and washed with water or sodium chloride solution. The 4-nitrosodiphenylamine hydrochloride thus obtained can be transformed into the free base by dissolving it in alkali, filtering from any residue and precipitating the base with acetic acid. This product crystallized from a mixture of benzene and petrol ether has a melting point of 145-146 C.

Example 2 169 g. of diphenylamine, equal to one gram mol,

is dissolved in 360 g. of methanol (commercial) by warming to 35-40" C. The solution is cooled to 0-5 C. and

'80; g. of finely divided sodium nitrite are added to the mixture. 2-3 hours Then over a period of from 237 g. of phosphorus oxychloride is added at 0-5 C. The mixture is then stirred from 46 hours at 0-5 0., poured into 3000 cc. ice water, stirred one hour, filtered and washed with water or salt solution. The 4- nitrosodiphenylamine hydrochloride thus obtained can be transformed into the free base by dissolving it in alkali, filtering from any residue and precipitatin the base with acetic acid. This product crystallized from a mixture of benzene and petrol ether has a melting point of 145146 C.

Having now described my invention and the present to generate hydrogen chloride and maintain the reaction mixture in a substantially anhydrous condition.

2. The process of producing a C-nitroso diarylamine which comprises introducing into an aliphatic alcohol media containing an alkali metal nitrite and an unsubstituted diarylamine, a

chlorine containin compound selected from the class consisting of phosphorus trichloride and lphorphorus oxychloride at a temperature not exceeding 30 C. while utilizing said chlorine containing compound to react with the water present in the reaction mixture to produce hydrogen chloride and maintain the reaction mixture substantially anhydrous, drowning the reaction "mixture in an ice water mixture and isolating the C-nitroso diarylamine.

3. The process of producing a C-nitroso diarylamine which comprises reacting at a temperature not exceedin 30 C. an unsubstituted diarylamine and an alkali metal nitrite in methanol in the presence of phosphorus oxychloride while utilizing the phosphorus oxychloride to react with the water present to produce hydrogen chloride and maintain the reaction mixture substantially anhydrous, drowning the reaction mixture in an ice water mixture and isolating the resulting C-nitroso diarylamine.

4. The process as defined in claim 1 wherein the aliphatic alcohol media is commercial methanol.

5. The process of producing a C-m'troso diarylamine which comprises introducing phosphorus oxychloride at a temperature not exceeding 30 C. into a suspension of an unsubstituted diarylamine and an alkali metal nitrite in commercial methanol while utilizing the phosphorus oxychloride to react with the Water present to produce hydrogen chloride and maintain the reaction mixture substantially anhydrous, drowning the reaction mixture in an ice water mixture and isolating the resulting C-nitroso diarylamine.

6. The process of producin a C-nitroso diarylamine which comprises introducing phosphorus trichloride at a temperature not exceeding 30 C. into a suspension of an unsubstituted diarylamine and an alkali metal nitrite in commercial methanol while utilizing the phosphorus trichloride to react with the water present to produce hydrogen chloride and maintain the reaction mixture substantially anhydrous, drowning the reaction mixture in an ice water mixture and isolating the resulting C-nitrosodiarylamine.

7. The process as defined in claim 1 wherein the unsubstituted diarylamine is diphenylamine.

8. In the process of producing a C-nitroso diarylamine by reacting at a temperature not exceeding 30 C. an unsubstituted diarylamine with an alkali metal nitrite in an aliphatic alcohol in the presence of hydrogen chloride, the improvement which comprises generating the hydrogen chloride in the reaction mixture by the addition thereto of a chlorine containing compound selected from the class consisting of phosphorus trichloride and phosphorus oxychloride, the chlorine containing compound operating to maintain the reaction mixture in a substantially anhydrous condition.

STILES M. ROBERTS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,495,774 Roberts Jan, 31, 1950 OTHER REFERENCES Parkes et al., Mellors Modern Inorganic Chemistry, Longmans, Green 8: Co., New York,

N. Y., new edition, 1939. p. 736 and 73s. 

1. THE PROCESS OF PRODUCING A C-NITROSO DIARYLAMINE WHICH COMPRISES REACTING AN ALKALI METAL NITRITE IN AN ALIPHATIC ALCOHOL MEDIUM WITH AN UNSUBSTITUTED DIARYLAMINE IN THE PRESENCE OF A CHLORINE CONTAINING COMPOUND SELECTED FROM THE CLASS CONSISTING OF PHOSPHORUS TRICHLORIDE AND PHOSPHORUS OXYCHLORIDE AT A TEMPERATURE NOT EXCEEDING 30* C. WHILE UTILIZING SAID CHLORINE CONTAINING COMPOUND TO REACT WITH THE WEATER PRESENT TO GENERATE HYDROGEN CHLORINE AND MAINTAIN THE REACTION MIXTURE IN A SUBSTANTIALLY ANHYDROUS CONDITION. 